Rewrite arg parser

[tk755]

Currently the command syntax q [command] TEXT [options] requires all commands to take input text, and all options to be boolean flags.

Rewrite the arg parsing logic to enable the following features:

• Commands are not required to take input text. This will unblock the following issues:
  • Enable -s with no input text to read previous command output #4
• Options can take arguments. This will unblock the following issues:
  • Add -f option to read input from an input file as context #5
  • Replace -o with -z and take an integer number of conversation turns to undo #7
• Enable certain options to run without commands or input text. This will unblock the following issues:
  • Allow -v to run alone #12
• Re-order the command syntax to q [options] [command] [TEXT] to continue enabling entering input text without requiring quotes.